Line 20 cm square baking pan with plastic wrap. In 3 litre microwavable bowl, combine corn syrup and evaporated milk, stir until well blended. Microwave on HIGH 3 minutes, Stir in chocolate chips until melted. Stir in confectioner's sugar, vanilla and walnuts. With wooden spoon, beat until thick and glossy. Spread into prepared pan. Refrigerate 2 hours until firm. 25 squares.